A variety of energy sources have been utilized to create therapeutic lesions in the human body. These energy sources include radio frequency, ultrasound, microwave and cryo. Recently it has also been demonstrated that diode laser energy can be used for these purposes.
Cardiac tissue is often the target of such energy applications for the treatment of various arrhythmias (abnormal rhythms of the heart). One such arrhythmia is atrial fibrillation. In treating atrial fibrillation, lesions in the walls of the heart are created to subsequently produce scar tissue. The scar tissue blocks errant xe2x80x9celectricalxe2x80x9d signals from propagating through the atrium or redirects the signals to the A-V node so as to restore the normal rhythm.
Traditionally the use of lasers in medicine has been through devices that deliver a single, narrow beam of light forward to vaporize (destroy) tissue. In cardiology applications such as atrial fibrillation, this has given rise to the concern for the potential risk of tissue perforation by the beam of light. Sinofsky in U.S. Pat. Nos. 5,908,415 5,643,253 and 4,878,492 disclosed devices and methods for the controlled and uniform delivery of light (photonic) energy to target tissue. This type of delivery also eliminates the risk of wall perforation by a beam of light.
The primary mechanism by which photonic energy functions is rapid and volumetric absorption by the tissue to cause coagulative necrosis. It does not rely on conductive heating from a burst of energy that occurs at the interface of the device and tissue. Peak temperature and absorption is below the tissue surface, avoiding tissue disruption at the catheter tissue interface. This clean formation of the lesion can avoid surface issues such as carbonization and clot formation. Appropriate use of parameters such as power and time help in the avoidance of these complications.
Another concern is that current ablation procedures for atrial fibrillation can be lengthy to perform. This is due largely to the limitations of current technologies in efficiently producing complete lines of conduction block without several tedious applications of energy. The use of laser devices propose the ability to quickly create a long transmural lesion (less than two minutes) with far fewer applications of energy. Thus the required ablating time is potentially greatly reduced.
It has been learned recently that circumferential lesions in the areas of the pulmonary veins located in the left atrium may be useful in the treatment of atrial fibrillation. The most common approach (percutaneously) to the left atrium involves creating a path from the right atrium through the atrial septum, commonly referred to as a xe2x80x9cseptal puncturexe2x80x9d. Some of the challenges related to this approach and treatment include passing a relatively small diameter (2.67-4.67 mm) device through the septal puncture that is still able to create a relatively large (15-30 mm diameter) circular lesion. Another challenge stems from a potential complication of delivering energy inside the pulmonary vein known as xe2x80x9cpulmonary vein stenosisxe2x80x9d.
The present invention provides a catheter system for overcoming the shortcomings of the prior art and in particular addressing the foregoing issues in circumferential lesions for the treatment of atrial fibrillation.
The invention catheter system includes:
a rotatable shaft having two lumens, the rotatable shaft being rotatable about a longitudinal axis and having a distal end and a proximal end;
working tube passing freely in one lumen of the rotatable shaft, the working tube having a length with a proximal end and a distal end disposed outside the distal end of the rotatable shaft;
and an energy emitting element having one end fixed into the other lumen of the rotatable shaft and an opposite end extending from the distal end of the rotatable shaft and coupled to the working tube between the proximal end and distal end of the working tube, wherein upon rotation of the rotatable shaft the energy emitting element forms coils around the working tube and upon movement of the rotatable shaft toward the distal end of the working tube, the coils of the energy emitting element become larger in circumference such that a radially expandable portion of the catheter system is defined.
In the preferred embodiment the working tube has (1) a longitudinal area along its length for passage of a movable guide wire to position the catheter system in a biological vessel, and (2) centering means coupled to its distal end, for coaxially centering the working tube in the biological vessel. The centering means may include an elastomeric balloon or radially expanding arms or other suitable elements for centering the working tube in the vessel.
Also in the preferred embodiment the opposite end of the energy emitting element is coupled to the working tube adjacent the centering means, and the rotatable shaft is simultaneously rotated and moved distally (i.e., toward the distal end of the working tube). Further the coils of the energy emitting element that define the radially expandable portion of the catheter system preferably make contact with the walls outside of the biological vessel orifice. As such, desired circumferential (circular) lesions are created. Alternatively, the coiled energy emitting element makes contact with biological tissue inside a vessel and produces desired circumferential lesions.
The energy emitting element may emit radio frequency, microwave, cryo or ultrasound energy.
In another embodiment, the energy emitting element is slidably disposed in a coilable tube.